Angle piece for dental purposes

ABSTRACT

The invention is directed to an angle piece for dental purposes comprising a tool with cylindrical tool shaft (50), which tool is supported in the head part (1) transversely relative to the drive axis or axle and is securely connected with its drive gear wheel (5) and is interchangeable together with the latter and is characterized in that a head bearing (42) on the tool side, which head bearing (42) is insertable in the head part (1) in a form-locking manner, is rotatably and undetachably connected with the tool (4) and in that an outer screw sleeve (29), which is axially displaceable on the head shaft, partly overlaps the head bearing (42) in its inserted position. A construction of the invention provides that the opening of the screw sleeve (29) has a hollow cone (33) which is pressable against a corresponding outer cone face (49) of the head bearing (42).

The invention is directed to an angle piece for dental purposes,comprising a tool with cylindrical tool shaft, which tool is supportedin the head part transversely relative to the drive axle and is securelyconnected with its drive gear wheel and is interchangeable together withthe latter. In addition, the invention is directed to an apparatus forlocking this structural component group, particularly provided that theangle piece is an integral structural component part of the cylindricalhead shaft without projecting parts.

In a known angle piece of this type, according to U.S. Pat. No.4,268,252, a construction of the angle head is described according towhich the latter forms the closure of the cylindrical head shaft anddoes not project over its circular cross-section of the latter. Agraduated cross borehole of the head shaft forms the bearing surfacesfor the drilling tool formed from the tool shaft and the drive gearwheel fastened on the latter. The end face of the gear wheel on the toolside forms a spherical cap with a radius of curvature equal to theradius of the head shaft and, when the tool is employed, closes so as tobe flush with the casing surface of the head shaft. A cylindrical sleeveoverlaps the head shaft and the part of the angle head, can either berotated or axially displaced on the shaft and is provided with openingswhich, according to the detail shown, either free the cross borehole ofthe head shaft or partially cover it. as desired, in order to make itpossible to introduce or hold the tool, respectively, in the workingposition. This construction of an angle piece head offers thepossibility of a very small manner of construction without projectingparts of the head, but it also involves disadvantages. For example,because of the fact that the bearing of the driven gear wheel connectedwith the tool shaft is effected in the cross borehole of the angle pieceshaft, the diameter of the bearing on the tool side is attached to thelargest diameter of the gear wheel in order to be able to remove thedrive from the head. This bearing is therefore greatly heated duringoperation at the high speeds usual today and, moreover, this has theresult that the entire head shaft must be replaced during the necessaryreplacement after wear, which means costly repairs. In addition, it isdisadvantageous that the gear wheel member does not have a sufficientflat bearing frontally against the tool, since its spherical end facehas line contact against the wall of the locking sleeve at only twoplaces at best and rapid wear will result at this place. A furtherdisadvantage is to be seen in that the longitudinal or transverse slotsprovided for passing the tool shaft in the locking sleeve interrupts theend bearing surface of the gear wheel drive, wherein the edges of theslot act on the rotating end face of the gear wheel like scrapers andcause the highly undesirable emergence of lubricant in the direction ofthe tool. Finally, it must be mentioned that in order to change the toolthe locking sleeve embracing the head shaft must be turned or axiallydisplced by hand and that it can be very troublesome to handle thisthin, smooth sleeve in the small dimensionings of the structural typeindicated, particularly because this sleeve must be fixed in its workingposition by means of friction so that it can not loosen unintentionallyand because, in addition, the outer casing of this sleeve serving as ahold is moistened by saliva during practical use and this makes manualhandling difficult. This deficiency becomes especially clear when it ismentioned that the locking sleeve of such an angle piece has an outerdiameter of 6 mm at most; that is, it is substantially thinner than apencil.

It is the object of the present invention to avoid the disadvantages ofthe known angle pieces with respect to the bearing and replacement ofthe drilling tool, as well as the disadvantages of the lockingapparatus, without restricting the possibilities of producing such anangle piece with a cylindrically smooth head shape, as well as inminiature constructional form. This is achieved, according to theinvention, in that a head bearing on the tool side, which head bearingis insertable in the head part in a form-locking manner, is rotatablyand undetachably connected with the tool and in that an outer screwsleeve, which is axially displaceable on the head shaft, partiallyoverlaps the head bearing in its inserted position. The head bearing,which is combined with the tool shaft, is rotatably supported with itsbearing borehole on a neck extension of the driven gear wheel, which islocated behind it and is securely connected with the tool shaft, and thehead bearing is held in position by means of a shoulder ring which ispressed on the tool side against the bearing cylinder of the gear wheeland overlaps this cylinder, and accordingly also the bearing borehole ofthe head bearing, in diameter. In order to fasten the bearing of thetool shaft in the assigned recess of the angle piece head axially aswell as radially in the operating position, the screwable sleeve, whichis rotatably supported on the head shaft, is provided, in a constructionof the invention, with an inner cone at its opening facing the tool,which inner cone can be joined and screwed on against a correspondingouter cone section attached on the tool bearing, wherein the action ofthe cone surfaces presses the bearing member axially, as well asradially, in its retainer. In order to be able to apply the requiredscrew forces without difficulty, it is suggested, according to theinvention, to construct the end of the screwable sleeve, which end isreinforced in diameter and is adjacent to the handle part of the anglepiece, as a longitudinally grooved turning handle which preferably formsthe transition of the handle part to the substantially smallercylindrical section of the angle head as a lengthened cone. In addition,it is suggested to construct the cylindrical part of the screwablesleeve, which cylindrical part acts on the tool bearing, and the anglepiece, which projects out over the latter, so as to have the same outerdiameter; this is shown with the aid of the drawings.

The invention is explained in more detail with the aid of the drawingshowing;

FIG. 1 a longitudinal section through the angle piece until the angledtransition to the handle part of same;

FIG. 2 a perspective view of an angle piece head, according to FIG. 1,with removed tool part;

FIG. 3 an angle piece head, according to FIG. 1, with inserted tool partand cylindrical front bearing, in section;

FIG. 4 an angle piece head as in FIG. 3, but with front bearing in theform of a semi-round head segment;

FIG. 5 an angle piece head, according to FIG. 4, with removed tool part,in perspective view.

The drilling tool 4 is rotatably supported in the head part 1 of anangle piece according to FIG. 1, which head 1 is connected with thehandle part 3 via an elongated cylindrical shaft 2, and is driven by apair of gear wheels 5, 6 which are driven in turn by the main axle 10via a shaft 7 penetrating the head shaft and a pair of gear wheels 8, 9arranged prior to the shaft 7. The handle part 3 and main axle 10 areconnected in a generally known manner with motor drives, as a rule, bymeans of detachable plug couplers.

The connection between the head shaft 2 and the angled handle part 3 isproduced by means of a threaded bush 11 which is screwed into the handlepart 3 by means of a threaded projection 12 and receives the head shaft2 and its bearing 15 on the handle side in a through-going graduatedborehole 13, 14, the bearing 15 on the handle side being screwed withthe head shaft via a thread 16 and overlapping the threaded neck 12 ofthe bush 11 with a flange 17. The flange 17 is clamped between thethreaded neck 12 and the annular step 18 of the handle part 3, for whichpurpose a slight air gap 21 is provided between the adjacent end faces19 and 20 of the parts 3 and 11 when screwing together the latter.Accordingly, when screwing together the parts 3 and 11 the head shaft 2is fixed in its position relative to the angled handle part 3, whereinconsists the possibility of selecting the position of the tool axis ofthe angle head 1 relative to the angular plane of the handle part 3 asdesired prior to screwing together the parts 3, 11, since head shaft 2and bearing member 15 are rotatably supported in the graduated borehole13, 14 of the threaded bush 11 with a narrow sliding fit. The axialpositioning of the shaft 7 results in that this shaft is reduced to asmaller diameter at its entrance into the rear bearing 15 and issupported against the bearing with the annular shoulder formed therebyand is held in this position by means of the drive wheel 8 mounted onthe shaft extension 22. The bearing 23 on the head side is mounted onthe shaft in the same manner, but is not securely connected with thehead shaft 2, being, instead, displaceably supported in its borehole 24.Bearings 15 and 23 are provided with axial passages 25 serving to allowthe passage of oil which is sprayed into the handle part of such anglehand pieces from spray bottles when subsequently lubricating these andall other bearings according to current practice.

With a tapered section 26, the threaded sleeve 11 forms the extension ofthe handle part 3 and ends on the head side in a threaded extension 27which can be screwed into the female thread 28 of a rotationally movablesleeve 29 supported on the head shaft 2. This sleeve forms thetransition from the angle head 1 to the tapered shaping of the threadedbush 11, engages in an annular groove 30 of the threaded bush 11,passes, with a tapered section 31, into a cylindrical part 32 which hasthe same diameter as the head 1 and whose bore opening can be made tocontact at the transition between head shaft 2 and head 1 with an innercore 33 against the likewise conical annular step 34. The sleeve 29 isprovided with gripping grooves 35 on the cone casing 31, which grippinggrooves enable the sleeve 29 to be turned by hand so as to screw and tobe tightened against the head. The depth of the annular groove 30 isdimensioned in such a way that the sleeve 29 can be screwed away fromthe head 1 until the cone projection 34 of the head is released, asshown in FIG. 2.

A graduated borehole, which is formed from a blind hole 36 and a largerborehole 37, is arranged in the head 1 so as to be transverse relativeto the drive axle, wherein the borehole 37 extends in the direction ofthe tool and passes into the borehole 36 in the center of the head abovea plane surface 38. The two boreholes are connected with the driveborehole in order to permit the tooth engagement of the drive wheels 5,6. A pin 39 is fastened in the head near the plane surface 38transversely relative to the borehole 37 and opposite the gear wheel 6and projects into the borehole 37. A slide bearing 40 is fastened in theblind borehole 36, the inner diameter of which slide bearing 40 isadapted to the shaft diameter of the drill and is closed at the base ofthe borehole by means of a wall 41 in order to axially support the drillshaft. A potlike bearing 42 of a cylindrical basic shape is detachablyheld in the borehole 37, strikes against the graduated surface 38 andcloses with the outer diameter of the head 1. An inner collar 43 of thisbearing forms the closure, on the tool side, of the angle piece head andthe front bearing of the latter simultaneously in that itsthrough-borehole 44 receives a cylinder neck 45 of the head drive 5 soas to allow rotational movement and also axially supports the drive 5.The hollow space 46 of the bearing member 42 is formed by means ofcylindrical bores or recesses which are somewhat larger than thediameter of the gear wheels 5, 6 projecting into the bearing member. Aslot 47 penetrates the sleevelike wall of the bearing 42 and is made toengage with the pin 39 in order to secure the bearing against turningand in order to be able to insert this bearing in the head infundamentally only one and the same position, respectively. In order tohold the bearing 42 in position a tapered chamfer 49 is arranged on itsend face 48, the casing surface or generated surface of which chamfer 49corresponds with the hollow cone 33 of the sleeve 29 and projectsslightly over the cone projection 34 of the head with reference to thedrill axis in the direction of the sleeve 29 and the sleeve 29 can nowbe screwed against the chamfer 49. The force effect via the cones 33, 49results in that the bearing is held in position axially as well asradially, in that the force-locking connection is well-secured againstautomatic loosening as a result of the cone action and in that thebearing can not be turned out of its position during tightening andloosening of the screw connection as a result of the support by means ofthe pin 39.

The drilling tool 4 is securely connected with the head drive 5, whereinthe cylindrical shaft 50 of the tool projects over the drive at its endand is rotatably supported in the bearing 40 of the head in theoperating position. In addition, the front bearing 42 is rotatablysupported on the neck extension 45 of the drive wheel 5 by means of aring 51 fastened on the tool shaft 50 in that the ring 51 overlaps theneck of the drive wheel and prevents the bearing from falling from thedrive wheel. In this manner the tool shaft 50, drive wheel 5, frontbearing 42 and ring 51 are connected to form a constructional unit whichis inserted and exchanged in the head 1 only as a whole and whoselocking is effected by means of the clamping action of the screw sleeve29, as described above. It is particularly advantageous that the screwsleeve 29 be constructed so as to be reinforced at its end and providedwith gripping grooves because the manipulation for tool replacementthereby moves from the actual angle head in the direction of the handlepiece and can be carried out there with the necessary secure grippingmore easily than was previously known.

The described construction unit of the drill tool 4 is shown in FIG. 2in front of the opening of the angle head 1 and all described structuralcomponent parts can be seen there. In this illustration, the screwsleeve 29 is drawn in the position away from the head 1 and its coneface 34, which position sufficiently frees the head borehole 37 for thepurpose of introducing the tool and its bearing 42.

The front bearing 42 need not necessarily have the cylindrical basicshape previously described. Particularly when the angle head has aparticularly small dimensioning, as required for the treatment ofchildren or as also seems desirable in other cases of parts of the humanjaw which are extremely difficult to reach, and with respect to the factthat the bearing must always have a smaller outer diameter than the headdiameter, it seems advisable to reinforce this bearing and to constructit so as to be more compact than the cylindrical basic shape allows. Forthis reason it is suggested, according to FIGS. 4 and 5, to employ abearing member 52 whose external shape is a cut out section from theangle head 1. Accordingly, the bearing member is a semicircular cylindersegment lying transversely relative to the drill axis, which cylindersegment is insertable in an adequate recess with boundary surfaces 53,54 and 55 of the head 1 and is to be fastened there by means of theclamping action of the screw sleeve 29. The fastening is effected, asdescribed above, by means of the action of the inner cone 33 of thesleeve 29 against a tapered chamfer 56 of the bearing 52 and thepressing of the bearing is expected against the surfaces 53 and 54 ofthe head 1, wherein the bearing body is simultaneously centered relativeto the axis of the head. The centering action is made possible in thatthe cone 56 is constructed over the full semicircle of the bearingmember 52 and is therefore compulsorily drawn by the screw sleeve 29into its axial position. The bearing member 52 projects out somewhatfarther in the direction of the screw sleeve 29 than toward the othersides; it is thereby reinforced in the area of the cone face 56 and isasymmetrical with reference to the drill axis and can therefore only beinserted compulsorily in this position--but not so as to be incorrectlyturned by 180°--in the head. It is also no longer necessary to fix thebearing member by means of a pin as described in FIG. 3. The tool,together with the bearing 52, is shown in FIG. 4 in the operatingposition within the head 1. The drive and the bearing of the tool, aswell as its locking and replacement, are effected in a correspondingsense as shown in FIGS. 1-3.

In order to reduce the wear of the screw sleeve 29 at its hollow cone 33the opening of the sleeve on the head side can be advantageously formedby means of a ring 57 arranged in front of it and composed ofparticularly resistent material, which ring 57 is connected with thescrew sleeve 29 so as to be fixed or rotatable and it permits the screwsleeve itself to be produced, for example, from light metal or similarmaterial for reasons of weight reduction.

The invention is not limited to the embodiment forms described and shownby way of example and it allows for additional constructions andmodifications. Thus it is possible, for example, when the drive gearwheels are correspondingly dimensioned, to unite the bearing of the toolshaft placed in the head with the front bearing on the tool side, tointegrate them accordingly in the constructional unit of the tool and toconstruct them so as to be likewise interchangeable. In addition, rollerbearings can be employed in place of slide bearings; the bearing memberscan project forward over the head shaping or the angle head can belarger than the neck piece of the screw sleeve. It is also possible toattach seals at bearings or connection points or to arrage lines forsupplying cooling media, e.g. within the angle head or at its outersurface. Finally, the drive of the tool need not be rotating, but canalso be a rotating pendulum drive, such as is known for dental filingangle pieces and where various root canal files are used instead ofdrills.

I claim:
 1. Angle piece for dental purposes comprising a head shaft, ahead part, and a tool with cylindrical tool shaft, which tool issupported in the head part transversely relative to the drive axis ofthe head shaft, said tool securely connected with its drive gear wheeland interchangeable together with the latter, characterized in that ahead bearing (42) is rotatably and axially immovably connected with saidtool (4), wherein said head bearing is stationary when inserted in saidhead part, and in that an outer screw sleeve (29) which is axiallydisplaceable on the head shaft (2) partly overlaps said head bearing(42) in its inserted position.
 2. Angle piece according to claim 1,characterized in that the opening of said screw sleeve (29) has a hollowcone (33) which is pressable against a corresponding outer one face (49)of said head bearing (42), wherein said hollow cone (33) and said outercone face (49) extend at the same angle relative to the tool axis. 3.Angle piece according to claim 2, characterized in that said headbearing (42) has a cylindrical outer shape and said outer cone face (49)is arranged at the transition of the end face (48) on the tool side tothe cylindrical casing surface or generated surface (42).
 4. Angle pieceaccording to claim 1, characterized in that said head bearing (42) issecured against turning in the insertion position by means of a pin (39)arranged in said head part (1), which pin (39) engages in a slot (47) ofsaid head bearing.
 5. Angle piece according to claim 1 or 2,characterized in that the outer shape of said head bearing (52) is asegment of said head part (1) and said outer cone face (56) is arrangedon the end face of said segment, which end face faces said screw sleeve(29).
 6. Angle piece according to claim 1, characterized in that saidscrew sleeve (29) enlarges conically at its end which is remote of saidhead part (1) and is constructed as a turning handle (31).
 7. Anglepiece according to claim 1, characterized in that said head part (1) isconnected with said head shaft (2) and said screw sleeve (29) isconnected with a base part (11), wherein said base part (11) can bescrewed into said handle part (3).
 8. Angle piece according to claim 1,characterized in that the outer diameter of said head part (1) and theouter diameter of the section (32) of said screw sleeve (29) adjoiningsaid head part are of equal size.